1. Field of the Invention
The invention concerns a plug coupling for several hose connections, in particular for measuring, control or regulating lines of fluidic systems with high pressures of several hundred bar or low and varying pressures, for manual actuation, consisting of a plug piece and a socket piece.
2. Description of the Related Technology
Valve couplings, in particular valve measuring couplings for fluid systems with a high working pressure are arleady known; they consist of a coupling bushing under line pressure, in which a spring loaded and mechanically actuable check valve is located.
Valve couplings of this type are used, for example to establish testing or measuring connections to pressure lines, wherein usually the coupling bushing is installed fixedly with external threads on the pressure line of for example a hydraulic or pneumatic system. For the duration of the test or measuring operation a sealing nipple in the form of a hollow pin is screwed on by means of a union nut, said sealing nipple being fixedly joined to a hose. The couplings may be connected, for example under pressure, i.e. without deactivating the installation, by means of measuring lines with the corresponding measuring instruments. In case of the connection of fixedly installed devices, for example manometers, manometer selection switches and pressure switches, the flexible measuring hose may be laid in a manner similar to electric cables, so that no expensive pipe installation is necessary. By means of such measuring couplings the effective working pressures may be read directly on the hydraulic apparatus, without the need for the loosening of deration screws and screwed pipe connections.
Couplings of this type are employed in connection with highly different structural elements and controls of hydraulic or pneumatic systems. Following the release of the coupling connection, a protective cap is screwed onto the coupling bushing in order to prevent the penetration of dirt into the bushing of the coupling and to effect an additional sealing function in case the check valve installed in the bushing is not entirely tight.
Valve couplings of the aforementioned type known, for example from DE No. 27 56 084, wherein the valve bodies are in the form of cones or spheres. In this known valve coupling the valve body is arranged as a check valve on a compression spring, displaceable by said spring and comprising on its upper end a flow channel. The valve coupling is equipped with a gasket which also prevents rotation, the sealing function of which is, however, assured only if a corresponding hose or closure cap is screwed securely onto the bushing of the coupling with its sealing nipple.
If said cap is loosened or if such a cap does not exist at all--as for example in the case of a selective manometer switch--the pressure medium is sealed off only by the corresponding check valve. However, check valves for high pressure couplings of this type have as a result of their design a more or less strongly perceived lack of tightness and cannot be manufactured in series to be entirely tight in actual practice.
For hose connections in general hydraulics and for gas filling devices of hydraulic reservoirs such a design is adequate, but even here complaints relative to inadequate tightness are being encountered, if for example the caps are loosened on several valve couplings simultaneously to test several measuring locations simultaneously in succession with a measuring device, when in the case of hydraulic reservoirs, gas pressure testing devices are used without refilling means, or if the valve couplings are used to monitor combustible gases, etc.
The use of such valve couplings is not possible at all for selective manometer switches because there is constant leakage at the connections not in use. Attempts have already been made in connection with the aforementioned valve couplings to provide the check valve with rubber elastic seals or conventional O rings, but in spite of adequate initial tightnesses, positive results are not always obtained. With long measuring lines and large dead volumes in manometers or in the circulation connected with them, and particularly in the case of low viscosity liquids or high operating pressures, or in testing devices for hydraulic reservoirs, the hydraulic seal may be washed out due to the very strong flow of the medium present at the seal, generated by the large pressure difference created by the lifting of the valve.